CPT 2026 · Pathology/Lab

CPT 84591

Global XXX

Assay of nos vitamin

Effective 2026-04-01 Conv. factor $33.4009

No national RVU

Payment Methodology

Status Indicator

NCCI Partners

XXX

Global Period

No national RVU

This code does not have a national work RVU on the current Physician Fee Schedule. Pricing may be carrier-determined, non-covered, or tracked via a separate methodology.

CPT 84591 Billing & Documentation Guide

CPT code 84591 (Assay of nos vitamin) is classified under Pathology/Lab with a global period indicator of XXX. This code uses the No national RVU payment methodology rather than standard RVU-based Physician Fee Schedule pricing. Refer to the methodology notice above for billing implications.

When billing 84591, ensure documentation supports medical necessity and the specific components required for the code's level of service. For E/M codes, document MDM (medical decision-making) elements: problems addressed, data reviewed, and risk. For procedural codes, document the indication, technique, and any complications. Always verify NCCI edits before bundling 84591 with related codes; this code has 10 PTP bundling relationships on file (see table below).

Payment Status & Global Period

CMS Status Indicator

Statutory exclusion

Global Period

XXX

No global period (E/M and other non-procedural services)

MUE Limit (Medically Unlikely Edits)

Max units per beneficiary per date of service

Rationale: Clinical: Data

Adjudication: Date of Service (Clinical)

Source: CMS NCCI MUE Practitioner Services, effective 2026-04-01.

Submitting more than 1 units of 84591 for the same patient on the same date triggers automatic line denial unless an appropriate modifier and supporting documentation justify the higher quantity.

NCCI Bundling Edits, CPT 84591

Procedure-to-procedure (PTP) edits. If you bill any of these codes with 84591 on the same date of service, review the modifier indicator and payer policy before submission.

Partner Code	Relationship	Modifier Allowed	Rationale
96523	Column 1 (primary), can be billed with modifier	No	CPT Manual or CMS manual coding instruction
0038U	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code
82180	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code
82306	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code
82307	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code
82607	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code
82652	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code
84207	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code
84252	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code
84425	Column 2 (secondary), bundled into primary	Yes	Misuse of Column Two code with Column One code

Frequently Asked Questions, CPT 84591

What does CPT code 84591 mean? +

CPT code 84591 represents: Assay of nos vitamin. It's in the Pathology/Lab category with a global period of XXX.

What is the Medicare reimbursement for CPT 84591? +

This code does not have a national work RVU on the current Physician Fee Schedule. Pricing may be carrier-determined, non-covered, or tracked via a separate methodology.

What modifiers can I use with CPT 84591? +

Pathology and laboratory use modifier 90 (reference/outside lab), 91 (repeat clinical diagnostic test same day), 92 (alternative laboratory platform), and QW (CLIA waived test). Surgical pathology splits between 26 and TC where applicable.

What bundling edits apply to CPT 84591? +

This code has 10 NCCI PTP bundling relationships. See the NCCI Bundling section below for full list.